1. Field of the Invention
The invention relates to an isolation dimmer circuit structure, and more particularly, to an isolation dimmer circuit structure that can be connected to various types of traditional dimmer circuits to control LED light sources and further provides protection against reversed voltage polarities and overvoltage.
2. Description of the Prior Art
Among dimmer circuits used for traditional light source elements (such as incandescent lamps), one simple control method is to directly connect a variable resistor in series between a power supply and the light source element. The resistance of the variable resistor is changed as needed to control the current flowing through the light source element, thus controlling the brightness of the light source element.
Another approach involves converting an external AC power supply into a DC voltage (or PWM) control signal. By applying variable DC voltages (or the PWM signal) to a constant load (the traditional light source element), the brightness of the light source element can then be controlled.
Since traditional light source elements and LED elements are significantly different in terms of light-emitting principles and electrical characteristics, a traditional dimmer circuit cannot be applied directly on lightings using LEDs as the light source. If a traditional dimmer circuit is to be used for adjusting the brightness of a LED, then a converting circuit has to be specially designed according to the original control method (resistive, voltage or PWM type) used by the traditional dimmer circuit. The converting circuit is then coupled between the traditional dimmer circuit and the LED element to convert a control signal (changes in resistance, voltage or PWM) output by the traditional dimmer circuit into a control signal suitable for controlling the brightness of the LED element.
However, the above converting circuit typically has the following shortcomings:
1. Since the converting circuits are specially designed according to the control methods (resistive, voltage or PWM type) of the traditional dimmer circuits, so converting circuits for different types of dimmer circuits have to be developed separately and cannot be used interchangeably. This lengthens the development time course and increases the cost, so it is not economical.
2. During the assembly process of the converting circuit and the traditional dimmer circuit, if there is an operational error (e.g. voltage polarities are reversed) or usage error (e.g. voltage is too high), circuit components may be damaged. In order to prevent such damages, a complicated protection mechanism (circuit) is required in the converting circuit. This kind of protection mechanism (circuit) will inevitably increase the overall cost.
In view of the shortcomings in the conventional converting circuits when in actual use, the present invention is proposed to effectively reduce the production cost and increase foolproof protection.